I've added some documentation on how activities and events for attacks are handled for a ZC character. I've still got some more stuff to document, but if anyone is planning on creating NPC's or exporting static props with lightmaps and needs a hand, this is the place to ask... so please keep this thread's conversations related to the exporter and compiler.

You mentioned creating new npcs in the first post. Is it possible to create a new npc_ entity without the need for programming?

You can change an existing NPC so it is completely different. If you change the info in the manifest you can even change the name and the display icon. You'd only require code to add an extra NPC or change the game logic. If you need more help post the specific questions and we can guide you.

I wasn't planning on doing any modelling myself (because I don't have the software and I know how).I might try using some of the human models from the Source SDK for what I'm doing. Did you change the .smd format in any way?

I've managed to compile a Half-Life 2 .mdl from the Source SDK with only a small change.Are the basic npc activities and sequences for Zeno Clash the same as Half-Life 2 e.g. ACT_WALK etc?

A few are, but many are not. For a description of ZC attack activities look at the wiki. (Here)

...now that I think of it... you need many activities that character models of HL will not have (such as close combat walk animations and standing up from the floor). You will not be able to replace a character with a HL one unless you have those animations... and for that you need the HL model rigged to our base skeleton.

All this is if by 'basic npc' you mean a character with whome you can fight.